Although polyisoprene has many physical properties that make it ideal for certain types of medical devices, it can be challenging to use for medical injection closures because of stringent guidelines by various standards organizations, especially USP. For example, requirements for elastomeric closures in Type-I devices are different from those for Type-II devices. Elastomeric closures in Type-I devices are for aqueous preparations; in Type-II devices they are for nonaqueous preparations. Overall, according to updated USP <381> guidelines, Type-I closure requirements are more stringent than Type-I requirements, especially for ultraviolet radiation absorbance and reducing substances.
Most traditional polyisoprene compounds meet Type-II requirements, but have difficulty meeting the updated physiochemical requirements for Type-I closures. Medical device manufacturers would benefit from having one type of polyisoprene that complies with both Type-1 and Type-2 requirements—which is now possible with Parker’s new polyisoprene compound RJ651-30.
Advanced polyisoprene is USP-compliant
In 2012 Parker research chemists formulated a new polyisoprene compound—RJ651-30—that complies with USP <381> guidelines for both Type-I and Type-II devices. Other key properties include:
- Superior tear resistance, elongation, rebound resilience, elastic modulus, low compression set, and stress relaxation when compounded with reinforcing fillers, plasticizers, cure systems, and other specialty ingredients
- Unique ability to reseal itself after being punctured, making it suitable for septa and closures for injection fluid-transfer applications
- Performs exceptionally well according to the functionality guidelines described in USP <381>, including penetrability, fragmentation, and self-sealing capacity tests using 21-gauge needles
- Meets Type-I absorbance guidelines (< 0.2 UV absorbance)
Exceeding USP requirements
When a needle pierces an elastomeric septum such as a vial cap closure or an IV bag port, it passes through the seal that protects the inner sterile environment from the outer environment. A properly designed elastomeric septum must allow easy needle penetration while maintaining the integrity of the seal at all times. It must also resist fragmenting, coring, or crumbling to prevent contamination and occlusions, while still being able to reestablish the seal when the needle is removed.
RJ651-30’s self-sealing capacity performance exceeds the level required in USP <381>. To further define the material’s limits, Parker researchers tested the material using 16, 18, 19, and 20 gauge needles—no trace of dye was passed in any of these tests (a 16-gauge needle has a cross-sectional area that is four times larger than a 21-gauge needle).
A self-sealing capacity test was performed by piercing the vials 10 times using 20-gauge needles and then placing them under vacuum. The vials were then stressed further by piercing them once, placing them immediately under vacuum, and repeating that process multiple times. All but one of the 10 vials tested in this manner survived 20 cycles (the single failed vial lasted five cycles).
In summary, Parker’s advanced polyisoprene material RJ651-30 meets or exceeds all USP <381> requirements for both Type-1 and Type-2 medical devices, simplifying material procurement, increasing operational efficiencies, and reducing overall cost. Because of its excellent mechanical and physical properties, RJ651-30 is an ideal material for injection septa and medical injection closures in Type-1 and Type-2 medical devices.
This article was contributed by Saman Nanayakkara, Engineering Manager, Parker Hannifin Composite Sealing Systems Division.
Visit Parker's Composite Sealing Systems Division website to learn more.